geostatistical analyst - an introduction · pdf file · 2014-06-06isaaks &...

Esri UC2013 . Technical Workshop .

Technical Workshop

2013 Esri International User Conference July 8–12, 2013 | San Diego, California

Geostatistical Analyst - An Introduction

Steve Lynch and Eric Krause Redlands, CA


Presentations of interest… • EBK – Robust kriging as a GP tool

- Wednesday 10:00am – 10:30am Demo theater

• Surface Interpolation in ArcGIS - Wednesday 4:30pm – 5:30pm Demo theater

• Areal Interpolation – Performing polygon-to-polygon predictions - Wednesday 5:30pm – 6:00pm Demo theater

• Geostatistical Simulations - Applications in Worst Case Scenarios - Thursday 11:00am – 11:30am Demo theater

• Designing and Updating a Monitoring Network - Thursday 11:30am – 12:00pm Demo theater

• Concepts and Applications of Kriging

- Tuesday 10:15am – 11:30am (room 04)

- Wednesday 3:15pm – 4:30pm (room 04)

• Creating Surfaces - Wednesday 8:30am – 9:45am (Room 03)

• Geostatistical Analyst - An Introduction • Tuesday 8:30am – 9:45am (room 05 A)

• Wednesday 1:30pm – 2:45pm (room 05 A)



Outline

• What is • geostatistics? • Geostatistical Analyst?

• New in 10+ • Interpolation workflow • Demonstrations • Supplementary information • Questions / Answers


What is geostatistics ?

Range

Sill

Nugget

The statistics of spatially correlated data

Semivariogram


Semivariogram

Semivariogram(distance h) = 0.5 * average [ (valuei– valuej)2]


What is geostatistics ?

The statistics of spatially correlated data


Geostatistical Analyst - Overview • Interactive

- Exploratory Spatial Data Analysis tools - Variography - Kriging - Other interpolation methods - Cross validation

• Geoprocessing toolbox - Interpolation - Sampling Network Design - Simulation - Utilities - Conversion


Where is Geostatistical Analyst used?



• 12 independent reputable geostatisticians • Given the same data • Asked to perform the same straightforward estimation

• Results were widely different • Different

- data analysis conclusions - variogram models and choice of kriging type - searching neighborhoods.

Experiment conducted by the US EPA 20 years ago

Isaaks & Srivastava, 1989. An Introduction to Applied Geostatistics.


Geostatistical Analyst – Toolbar and Toolbox


Demonstration Geostatistical Wizard


What’s new in 10 – Optimize buttons • Local Polynomial Interpolation • Kriging

- Nugget, partial sill and other(s), are optimized using cross validation with focus on the estimation of the range parameter.


What’s new in 10.0+ • Areal Interpolation

- predictions can be made from one set of polygons to another set of polygons

• Empirical Bayesian Kriging (EBK) - builds local models on subsets of the data,

which are then combined together to create the final surface.

• Normal Score Transformation - Multiplicative Skewing approximation method


Interpolation workflow • Exploratory Spatial Data Analysis (ESDA) • Interpolate

- estimation of values at unsampled locations based on known values

• Goodness of fit



Exploratory Spatial Data Analysis • Where is the data located? • What are the values at the data points? • How does the location of a point relate to its value?


Exploratory Spatial Data Analysis (ESDA)


Kriging

• Concepts and Applications of Kriging - Tuesday 10:15am – 11:30am (room 04) - Wednesday 3:15pm – 4:30pm (room 04)

• Empirical Bayesian Kriging – Robust kriging as a GP tool - Wednesday 10:00am – 10:30am Demo theater

Outline • Introduction to kriging • Best practices • Fitting a proper model • Variography, transformations, isotropy, stationarity • Comparing models using cross validation • Interpreting results



What is kriging? • It is a geostatistical interpolation technique

• that models the spatial correlation of point measurements

• to estimate values at unmeasured locations.

• Associates uncertainty with the predictions

DistanceC

orre

latio

n



Demonstration Kriging


Empirical Bayesian Kriging (EBK)

• automates the most difficult aspects of building a valid kriging model

• estimates the semivariogram through repeated simulations

• can handle non-stationary input data. Unlike other kriging methods (use weighted least squares), the

semivariogram parameters in EBK are estimated using restricted maximum likelihood (REML).

New in ArcGIS 10.1



For a given distance h, the semivariogram model: γ(h)= Nugget + b|h|α



Empirical Bayesian Kriging (cont)

• Advantages - Requires minimal interactive modeling - Allows accurate predictions of non-stationary data - More accurate than other kriging methods for small datasets - Geoprocessing tool

• Disadvantages - Processing is slower than other kriging methods. - Cokriging and anisotropy are unavailable.



Demonstration Empirical Bayesian Kriging


Goodness of fit / Model acceptance

• Subset Features • Cross Validation



Cressie, 1990

• Cross validation does not prove that the model is correct,

• merely that it is not grossly incorrect.


Demonstration Cross validation


Geostatistical layer

• Method and parameters • Pointer to the data • Dynamic


Output = Prediction, Prediction SE, Probability, Quantile, Condition number


Demonstration Geostatistical layer


Areal Interpolation

• reaggregation of data from one set of polygons to another set of polygons

New in ArcGIS 10.1



Demonstration Areal Interpolation


Areal Interpolation Wednesday 5:30pm – 6:00pm

Demo theater


N = 8 N = 100 N = 500

Simple kriging



Geostatistical Simulations Thursday 11:00am – 11:30am

Demo theater


Interpolation with Barriers

• Kernel interpolation • Diffusion interpolation

? Cost Raster



Create Spatially Balanced Points

Sampling Network Design

• Monitor road pollution • Convert roads to raster • High value = busy road • Low value = quite road


Create Spatially Balanced Points (cont.)



Densify Sampling Network


• Used kriging to create: - Prediction surface - Standard error of prediction

• Want to add 2 new sites


Densify Sampling Network (Cont.)



Designing and Updating a Monitoring Network Thursday 11:30am – 12:00pm

Demo theater


resources.arcgis.com

Esri UC2013 . Technical Workshop . Geostatistical Analyst - An Introduction


http://esripress.esri.com


Please fill out the session evaluation

First Offering ID: 1174 Second Offering ID: 1294

Online – www.esri.com/ucsessionsurveys Paper – pick up and put in drop box

Thank you…

geostatistical analyst - an introduction · pdf file · 2014-06-06isaaks &...

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